What material category does Class 4 refer to?

Class 4 refers to flammable solids. This classification includes materials that can ignite easily and burn rapidly when exposed to an ignition source. Flammable solids can include items such as certain types of metals, powders, or materials that are readily combustible and can create hazardous conditions if not handled or stored properly.

Understanding this classification is crucial for safety in transportation and storage, as flammable solids pose significant risks of fire and explosion in various environments. The other categories represent different types of hazardous materials: explosives are classified separately due to their potential for detonation, toxic and infectious substances require careful handling because of health risks, and oxidizers enhance the combustion of other materials, necessitating their own distinct classification.